What are autoimmune thyroid diseases? Autoimmune thyroid diseases, such as autoimmune thyroiditis, which is also known as Hashimoto’s thyroiditis or chronic lymphocytic thyroiditis, are conditions in which the immune system attacks the body’s own thyroid gland. The thyroid gland, which is a small gland at the front of the neck, becomes chronically inflamed and decreases production of the thyroid hormones triiodothyronine and thyroxine. Because these hormones are used almost everywhere in the body, autoimmune thyroid diseases can have widespread, serious effects and many symptoms. Autoimmune thyroid diseases are generally hereditary in origin, although environmental factors, such as infection, certain drugs, and iodine consumption, can play a role in their progression. Autoimmune thyroiditis is more common in women than in men, and it primarily affects people between 40 and 60 years of age. Like many autoimmune disorders, your chances of getting autoimmune thyroiditis are increased if you have other autoimmune disorders. Often, mild autoimmune thyroiditis can be symptomless. In more serious cases, however, inflammation of the thyroid can lead to enlargement (goiter). Over time, the thyroid can suffer more damage, leading to symptoms of hypothyroidism (underactive thyroid), such as fatigue, weight gain, body aches, depression, and lethargy. Autoimmune thyroiditis may not always require treatment. For those who do experience problematic symptoms, treatment is generally in the form of synthetic thyroid hormones. Generally, the disease is slow to progress and can remain stable for many years without complications. While chronic autoimmune thyroid diseases are generally mild or even symptomless, they can progress to significant hypothyroidism. Seek prompt medical care for worrisome symptoms of hypothyroidism, such as depression or unexplained weight gain.